I recently helped a friend remove a 454 Mercruiser engine, pull the heads, freshen up the heads (valve lap and new valve seals), re-assemble the engine, and install it back in the boat. The engine had sat for awhile and I recommended new bearings, a cylinder wall hone, and new rings (rings and bearings are pretty cheap and I have all the tools needed) while it was on a stand in my garage, but my friend did not want to do that...

When we first started it and brought it up to operating temperature, it was blowing blue smoke and clearly burning oil; and also has quite a bit of blow-by. Looked like a classic case of stuck rings to me (the cylinder bores were nice, and had little wear). The second time we started it and brought it up to temperature, the smoke was gone but the blow-by remains. He will be water-testing it tomorrow. I suspect that under load the rings will probably loosen up and the blow-by will diminish dramatically. Anyone have experience with this happening?

Before starting, you might try pouring a bit of Marvel Mystery Oil in each cylinder and let it be for a day or two. It should help out with the stuck rings and keep from scoring the cylinders or rings. But, maybe the damage has already been done.

http://www.marvelmysteryoil.com/

Just wondering if he/you removed the pistons from the cylinders during the re-build, or did the lower-end of the engine stay intact? Also, there is the theory of a tighter top-end (valves) will cause additional pressure on the lower-end (rings) and contribute to blow-by/oil burning after a rebuild.

The guy should have really taken your advice as the lower end of the engine may be short lived. How many hours total on the engine?

A little too late, I imagine.

Good friend that owned a machine shop told me years ago that you are way better off just doing it right the first time. Of course he told me that after we rebuild the top end of the motor in my Trans Am only to blow the bottom end days later. Some lessons you just have to learn the hard way.

We did not remove the pistons, didn't even drain the oil. Only reason we took the engine out was because three head bolts (the ones just oudside the valve cover needed to be drilled (that is some hard steel...) because the heads were rusted to little useless nubs from an exhaust elbow leak.

Looks like a low hour late 80s gen IV 454 to me. There was no ridge at all on any cylinder wall. Had it been my engine, the pistons would have come out. Rings, honing and bearings would have been about 8 more hours of labor at the most and the engine would be like new. Oh well, not my problem... My gut says it will probably be fine after running with a load. No load will not cause much cylinder pressure.

Dave -

Also, I got a couple of 454 engines in my boat that are getting up to 1,000 hours on them. Probably will lap the 1,000 hour mark this season. Wondering if I should pull the engines for a rebuild or wait a bit longer Probably will do a full regiment of compression and leak tests this Fall, when the boat comes out.

Maybe if you have got some time on your hands over the winter . . . Just would have to figure how to get them out of the boat, since it is a lot higher lift than a typical bowrider or cuddy.

My "boat port" would be ideal for pulling your engines, I suspect. It has a lot of height and was built with this in mind. See https://www.facebook.com/media/set/...7.1591328395&type=1&l=a53b83846f Just have to get the boat here. If you want to store it here for the Winter, just pay to have my boat shrink-wrapped and I can park it elsewhere on my property. I have a big block capable engine stand as I'm sure you do as well.

That said, 1000 hours is nothing for a 454. Mine has nearly that and makes full power with no issues at all. When the time comes to rebuild, consider a .060" overbore and a 4.2"5 crank kit combined with beehive valve springs and a bigger marine cam. Should be able to squeeze an extra 120 HP out of each of them with ease.

Just cleaning the ring lands before reinstalling the rings would most likely have helped...

I'm with you on the extra effort having been worth it, especially on an engine that sat for awhile.

Thanks for the offer of the boat port. It would probably cost $2K to get my boat up there and back, so that would be an issue. I might see if I can get some more hours out of the engines and then build a gantry to lift them out of the boat. The rear seat/engine hatch assembly would have to come out first, and I have a feeling it weighs as much as one of the engines.

Try drowning the 454 with a couple cans of Seafoam, might de-crud the rings enough to help-

How long did the engine sit and was the problem there before sitting? Why did you pull the heads? Did it smoke all of the time, just when starting, under load? What type of valve seals did you use, Teflon, Viton, etc?? Lots of questions, sorry

Sat for a year, but was not fogged and had only run once briefly on a test stand prior to purchase. Prior to that, the history is a mystery. Had to pull one head to fix a stuck exhaust valve that was not an issue during the test run. I recommend new seals a valve seat lap while it was out of the boat so the owner did that, hence the removal of both heads. The seals are OEM style and orange if memory serves, no idea what they are made of. It smoked pretty bad upon start up and only diminished after a temperature cycle. He's run it on the water for a few hours now and the smoking did improve, but it does use some oil and still has blow-by. He'll be hitting it with Seafoam and marvel mystery oil this week.

I came up with an idea to free the rings on my friend's boat.

1. Mix 2 gallons of gas with .6 gallons of Seafoam/Techron and .2 gallons of 2 stroke oil in a 2.8 gallon garden tractor fuel tank (I used 2.8 gallons because that's the size tank I have...)
2. Mark tank so that the level in it can be measured in 1/8 tank increments.
3. Run boat on water until it is fully warmed up.
4. Disconnect fuel inlet side of fuel pump from boat internal tank and run engine until it dies.
5. Connect my 2.8 gallon tank to fuel pump inlet so that the engine will run solely on my 2.8 gallon mixture.
6. Disconnect #1 plug wire from distributor cap and replace it with a plug wire that's solidly attached to ground.
7. Run engine at 1/2 throttle or more, under load, until 1/8 of the fuel mix is used up.
8. Reconnect #1 plug wire and repeat steps 6 and 7 for #2 plug wire.
9. Repeat steps 6, 7 and 8 for remaining spark plug wires to use up all the fuel mix and ensure each cylinder runs without spark for 1/8 of the time the fuel mix allows.
10. Once special fuel mix is exhausted, reconnect boat tank fuel supply line to fuel pump inlet.

My thinking is that the mixture will give the rings a good cleaning in all the cylinders regardless, but by removing spark from one cylinder at a time, that dead cylinder will get an especially good cleaning as the solvents will not be burning in that cylinder. The two stroke oil is there solely to provide some lube for the rings since the gas and other solvents will wash the cylinder walls of any motor oil.

Having come up with the idea, I, of course, think it's brilliant; lemme know what you think... I imagine the mix will smoke like crazy, so I'd do it on a week day, at night, away from other boaters.

Change the oil after.

I would do it anytime that works for you. If anyone complains just say you are fogging the mosquitos.

Good call.

If the rings are sticking, how about shooting some light oil (Marvel Mystery Oil) in the cylinder and wiggling the crank both directions a little bit.

Good thinking. No Marvel Mystery Oil? Any particular reason other than it is an unknown?

Dave this is a really good idea (IMO), and you came up with it on a holiday no less

I'm also thinking the method could be used as a general cylinder de-carb, as the solvents would not burn off in the 'idle' (non-firing) cylinder. I have gotten my engine to run with as much as 50% seafoam in the gasoline, but probably would not need that much. I might try this towards the end of the season to do a general clean-up in the cylinders